 
(* ::Section:: *)
(* $MU *)
(* ::Text:: *)
(*$MU is the head of dummy indices which may be introduced by Chisholm, Contract, DiracSimplify, FermionSpinSum and various QCD functions. By default it is unset, but can be set to anything..*)


(* ::Subsection:: *)
(* See also *)
(* ::Text:: *)
(*Chisholm, Contract, DiracSimplify.*)



(* ::Subsection:: *)
(* Examples *)



$MU
